This proposal explores cell signaling pathways that occur between cutaneous sensory nerve fibers and endothelial cells during response to cutaneous injury. With increased patient survival following large burn injuries, disability due to hypertrophic scar formation has become an important clinical problem that affects as many as 100,000 patients per year in the United States. This abnormal response to injury results in significant patient misery due to both the unsightly deformity and also devastating itching and pain. The scars have hypervascularity and increased innervation. In contrast, non-healing ulcers of diabetes mellitus have microangiopathy and decreased innervation. We anticipate that in hypertrophic scars increased endothelial cell proliferation and neurotrophin synthesis leads to the hypervascularity and pruritis. Our Iong term hypothesis is that followinq cutaneous injury, 1) sensory nerve fibers secrete neuropeptides such as substance P that regulate endothelial cell response to injury and 2) microvascular endothelial cells secrete neurotrophins that regulate nerve fiber regeneration. We will test our hypothesis by addressing the following aims: Aim 1: To determine intracellular mechanisms by which substance P regulates endothelial cell proinflammatory response. We will determine whether the substance P induces endothelial cell production of nerve growth factor, vascular endothelial growth factor and interleukin 8 by 1) G-protein coupled pathways or 2) cell shape change and cytoskeleton reorganization. Aim 2: To determine the role of nitric oxide synthase in substance P mediated response to injury by endothelial cells. We will determine whether substance P signaling pathways leading to nerve growth factor, vascular endothelial growth factor and interleukin 8 synthesis depend on nitric oxide. Aim 3: To determine which endothelial cell derived mediators regulate nerve cell sprouting. We will evaluate the second limb of our hypothesis by identifying endothelial cell-derived neurotrophins that regulate sensory nerve fiber sprouting. Using an in vitro model of nerve growth, we will verify that the manipulations in aims 1 and 2 diminish soluble mediators that are responsible for nerve differentiation. Aim 4: To determine how neuropeptide activity in transgenic mice and mutant diabetic mice alters response to injury. We will determine how substance P modulates cutaneous response to injury using an excisional wound model in normal mice, in diabetic mice and in mice with targeted disruption of neuronal nitric oxide synthase, inducible nitric oxide synthase or endothelial nitric oxide synthase.